1. Field of the Invention
The present invention relates generally to a computerized method and system provided to aid radiologists in detection of abnormalities, such as lung nodule, pneumothorax, pneumonia, and bulla, in chest radiographs.
The present invention also generally relates to computerized techniques for automated analysis of digital images, for example, as disclosed in one or more of U.S. Pat. Nos. 4,839,807; 4,841,555; 4,851,984; 4,875,165; 4,907,156; 4,918,534; 5,072,384; 5,133,020; 5,150,292; 5,224,177; 5,289,374; 5,319,549; 5,343,390; 5,359,513; 5,452,367; 5,463,548; 5,491,627; 5,537,485; 5,598,481; 5,622,171; 5,638,458; 5,657,362; 5,666,434; 5,673,332; 5,668,888; 5,740,268; 5,790,690; and 5,832,103; as well as U.S. patent application Ser. No. 08/158,388 (PCT Publication WO 95/14431); Ser. Nos. 08/173,935; 08/220,917 (PCT Publication WO 95/26682); Ser. No. 08/398,307 (PCT Publication WO 96/27846); Ser. No. 08/523,210 (PCT Publication WO 95/15537); Ser. Nos. 08/536,149; 08/562,087; 08/757,611; 08/758,438; 08/900,191; 08/900,361; 08/900,362; 08/900,188; 08/900,189, 08/900,192; 08/979,623; 08/979,639; 08/982,282; 09/027,468; 09/027,685; 09/028,518; 09/053,798; 09/092,004; 09/098,504; 09/121,719; 09/131,162; 09/141,535; and 09/156,413, all of which are incorporated herein by reference. Of these patents and applications, U.S. Pat. Nos. 4,907,156; 5,072,384; 5,224,177; 5,289,374; 5,319,549; 5,359,513; 5,463,548; 5,622,171; 5,790,690; Ser. Nos. 08/562,087; 08/562,188; 08/757,611; 08/758,438; 08/900,191; 08/900,361; 08/900,362; 09/027,685; 09/053,789; and 09/121,719 are of particular interest.
The present invention includes use of various technologies referenced and described in the above-noted U.S. patents and applications, as well as described in the references identified in the appended APPENDIX by the author(s) and year of publication and cross-referenced throughout the specification by numerals in brackets corresponding to the respective references listed in the APPENDIX, the entire contents of which, including the related patents and applications listed above and references listed in the APPENDIX, are incorporated herein by reference.
2. Discussion of the Background
Detection of early lung cancers on chest radiographs is a difficult task for radiologists, because subtle lesions tend to be low in contrast and can overlap with ribs and clavicles. To assist radiologists in the detection of newly developed abnormalities on chest radiographs, a temporal subtraction technique has been reported. [1] In this technique, a previous chest image is subtracted from a current chest image to produce a subtraction image. Subtle changes on chest radiographs can be enhanced on the subtraction image, and thus the detection accuracy of interval changes can be improved significantly by use of the temporal subtraction technique. [2] However, the temporal subtraction technique is not applicable in the absence of a previous chest radiograph.